With a power of 90%, a type I error probability of 5% and an estimated standard deviation of 25%, we should include 17 patients to detect a minimum relevant difference (MIREDIF) of 20% between brimonidine and control. We choose a 20% MIREDIF, since a reduction in inflammation <20%, based on a resource economic point of view is considered clinical irrelevant. Based on earlier experience and duration of the trial, a 15% dropout rate should be taken into account and therefore, a total of 20 patients will be included.